GCSE Computer Science Glossary

A

abstraction: Removing unnecessary detail from a problem so you can focus on the essential parts.
Accumulator: The result of calculations carried out by the ALU. (Data.)
algorithmic thinking: The ability to create a clear, step-by-step set of instructions (an algorithm) that solves a problem.
ALU: Performs arithmetic operations (e.g. addition, subtraction) and logical operations (e.g. AND, OR, comparisons).

B

bit: A single binary digit, either 0 or 1.
brute-force attack: Automated software trying many username/password combinations to guess login details.

C

cache: Small, very fast memory inside or near the CPU that stores frequently used data and instructions.
character set: A system that assigns a unique binary code to every character.
clock speed: The number of clock cycles per second, measured in hertz (Hz), usually gigahertz (GHz) for modern CPUs.
colour depth: The number of bits used to represent the colour of one pixel.
command line interface: An interface where the user interacts by typing text-based commands.
compression: Reducing the size of a file.
Computer Misuse Act 1990: Unauthorised access to, or modification of, computer material.
Control Unit: Coordinates the CPU by sending control signals to the other components and managing the fetch-execute cycle.
Copyright, Designs and Patents Act 1988: Original work (e.g. software, music, images) from being copied without permission.
cultural issues: How different groups, with different values/traditions/beliefs, view the same technology differently.

D

data compression software: Reduces file size, saving storage space and reducing transmission time.
Data Protection Act 2018: How organisations use people's personal data.
decomposition: Breaking a complex problem down into smaller, more manageable sub-problems.
defragmentation software: Reorganises a disk so each file's data is stored together, improving access speed.
denial of service (DoS) attack: Overwhelming a server with traffic so it becomes slow or unavailable to real users.
DNS: Converts a URL into the IP address of the server hosting the website.
driver: A small program that acts as a translator between the OS and a specific piece of hardware.

E

embedded system: A computer dedicated to a specific task, built into a larger device.
encryption: Scrambles data using a key, so it cannot be understood if intercepted without the correct key.
encryption software: Converts data into a coded format using a key, so it cannot be understood without that key.
environmental issues: The impact on the natural world: energy use, limited resources, and e-waste.

F

fetch-execute cycle: Fetch (get the next instruction), Decode (work out the operation), Execute (carry it out).
file management: Naming, saving, organising into folders, and moving/copying/deleting/renaming files.
firewall: Monitors traffic and blocks or allows it based on a set of security rules.
fragmentation: When a file's data becomes split into scattered pieces across a disk over time.

G

GUI: A graphical user interface: visual interaction using icons, windows and menus.

H

hosting: Storing a website's files on a server so that it can be accessed over the internet.

I

image: Colour depth x image height (px) x image width (px).

L

LAN: A network covering a small geographical area (e.g. one site or building), typically using owner-owned hardware.
layers: One layer can be changed without needing to change the other layers.
least significant bit (LSB): The rightmost bit, the one with the smallest place value (1).
logic error: An error that lets the program run, but produces an incorrect result.
logically ordered: Each character's code follows on from the last, so the code for 'B' is one more than the code for 'A'.

M

MAC address: A unique identifier permanently assigned to a device's network hardware.
malware: Software designed to cause harm or gain unauthorised access to a system.
MAR: The address of the memory location to be read from or written to. (An address.)
MDR: The data or instruction being transferred to or from memory. (Data.)
memory management: Allocates sections of RAM to applications and tracks what is in use.
mesh topology: No single point of failure, data can be rerouted if a connection fails.
metadata: Extra information stored with the image, such as its height and width.
more cores: Multiple instructions to be processed at the same time (in parallel).
most significant bit (MSB): The leftmost bit, the one with the largest place value (128 in an 8-bit number).

N

NIC: Allows a device to connect to a network.

O

open source: Software whose source code is publicly available, so anyone can view, modify and redistribute it.
operating system: To manage and control the computer so other software can run.
overflow error: When the result of a calculation needs more bits than are available to store it, so the extra bit is lost.

P

peer-to-peer: A network where all devices have equal status, with no dedicated server.
penetration testing: Deliberately attempting to gain unauthorised access to find vulnerabilities before real attackers do.
peripheral management: Managing the transfer of data between connected devices (peripherals) and the processor.
phishing: A fraudulent communication disguised as a trustworthy source, tricking victims into giving away private information.
physical security: Theft, tampering, or unauthorised physical access to hardware.
primary storage: Memory the CPU can access directly. It holds the data and programs currently in use, and usually consists of RAM and ROM.
Program Counter: The address of the next instruction to be executed. (An address.)
proprietary: Software owned by a company, source code kept private, usually purchased as a licence to use.
protocol: A set of rules for transferring data between devices.

R

RAM: The data, programs and operating system that are currently in use.
registers: Small, high-speed storage locations inside the CPU that hold data or addresses currently in use.
ROM: The start-up (boot) instructions the computer needs when it is switched on.
router: Connects separate networks together, e.g. a LAN to the internet.

S

server: It provides services (e.g. web pages, file storage) that clients request and use.
social engineering: Manipulating people into giving away confidential information.
sound: Sample rate x duration (s) x bit depth.
spyware: Secretly gathers information about a user (e.g. keystrokes, logins) and sends it to the attacker.
SQL injection: Entering malicious SQL code into a website's input field to gain unauthorised access to its database.
standard: A set of agreed rules that allows hardware/software from different manufacturers to work together.
star topology: Easy to add new devices; one cable failing only affects that device.
structure diagram: A diagram showing a problem broken into subsections and how they link together.
switch: Sends data directly to the device it is intended for, using MAC addresses. It does not store data or provide services.
syntax error: An error that breaks the rules of the programming language, stopping the program from running.

T

text: Bits per character x number of characters.
the Cloud: Remote services (storage, software, processing) provided over the internet.
trace table: To track the value of variables (and any output) as an algorithm runs, step by step.
trojan: Software that disguises itself as legitimate to trick the user into installing it, then gives an attacker access.

U

user access levels: Restrict users to only the data/features they need, limiting damage from misuse or a compromised account.
user management: Allocating accounts, setting access rights, and enforcing security.
utility software: Software that performs housekeeping tasks not carried out by the operating system.

V

virtual memory: An area of secondary storage used as extra memory (an extension of RAM) when RAM is full.
volatile: The memory loses its contents when the power is turned off.

W

WAN: A network covering a large geographical area, connecting multiple LANs, often using third-party infrastructure.